The present invention relates to a ramp mechanism for holding a suspension arm which holds a head for reading and writing of information from and to an information recording disk rotating at a high speed in an information recording disk apparatus in such a state as spaced from the disk when the disk is in its inoperable mode.
Among information recording apparatuses for use with an information processing apparatus such as a computer, a hard disk drive unit as an information recording disk apparatus, which uses a magnetic recording disk rotating at a high speed as a recording medium, rotates a plurality of magnetic recording disks (which will be referred merely to as recording disks, hereinafter) at a high speed, writes or reads information to or from each recording disk by means of magnetic heads provided as associated with upper and lower surfaces of each disk.
The magnetic head for use with the hard disk drive apparatus, which is supported to a suspension arm or the like driven by an actuator, moves on the recording disk at a high speed. Further, the magnetic head and recording disk are not contacted with each other, and the action of an airflow generated by rotation of the recording disk causes the magnetic head to float the recording disk over with a very small gap therebetween.
When the recording disk is not rotated with respect to the magnetic head, it is required for the magnetic head not to be brought into contact with the recording disk. This is because a long-time contact of the magnetic head with the recording disk not being rotated may undesirably result in the fact that the head to stick to the surface of the disk. In such a case, start of the rotation of the recording disk causes the head-stuck surface of the disk to peel off, thus resulting in a damage of the surface of the disk.
Even when the surface contact time between the magnetic head and recording disk is too short to cause such a sticking phenomenon as mentioned above, it is required that the head not be contacted with the disk. This is for the purpose of avoid such a situation as will be explained below. That is, for example, after the magnetic head came into contact with the recording disk being stopped in rotation, if the disk starts its rotation and reaches to a predetermined rotational speed, then a contact friction between the head and disk during that contact period may cause the surface of the disk to be scraped. In order that the magnetic head flies over the surface of the recording disk, it is generally required that the disk reach a predetermined rotational speed.
As mentioned above, so long as the recording disk does not reach the predetermined rotational speed, the head must be spaced from the disk. To realize this, there has been known in these years a mechanism for holding a magnetic head called a ramp which holds a magnetic head and a suspension arm relative to a recording disk with a gap spaced therefrom when the rotational speed of the recording disk is below the predetermined level.
In a recent hard disk drive apparatus, there is provided a ramp as a magnetic-head retraction location where the head is held as spaced from a recording disk when the disk stops its rotation or while it is rotating at a low speed. In such a hard disk drive apparatus, when the rotational speed of the recording disk is decreased to such a level that the head cannot float the disk over, the apparatus unloads the head; whereas, when the rotational speed is increased to such a level as to enough to float the head over, the apparatus loads the head onto the disk. Such a system of unloading and loading the head to and from the ramp as mentioned above is known as a ramp loading system.
The ramp is made of polymeric material, molded and manufactured. The ramp is fixed to a housing of the hard disk apparatus by means of screw, and is subjected to a stress in a compression direction when the ramp is pushed against the housing by a tightening torque of the screw. Accordingly after passage of a long period of time, the ramp made of the polymeric material is susceptible to a creep deformation as a plastic deformation.
Further, for the purpose of rotating the recording disk at a high speed, a motor, a driver circuit therefor, and so on are built in the information recording disk apparatus. Heat evolution of the motor, driver circuits, etc. will cause the internal temperature of the disk apparatus to inevitably increase. Thus even the ambient temperature of the ramp increases during the high-speed rotation of the disk, and decreases therefrom during rotation stoppage of the disk and approaches normal temperature. In other words, the ramp is used in a environment of temperature cycling. In this case, the creep deformation takes place more easily with time passage, as will be clear from the fact that, in a reliability test field for example, time is accelerated with temperature cycle.
FIG. 11(a) is a perspective view of a conventional ramp when all parts of the ramp are made of polymeric material containing polytetrafluoroethylene (PTFE) and are integrally molded. FIG. 11(b) is a enlarged perspective view of a front end edge part of a guide section for guiding a suspension arm in the ramp of FIG. 11(a). In FIGS. 11(a) and 11(b), the ramp is of a type wherein the suspension arms are held when three stages of recording disks for both side use are stacked.
As shown in FIG. 11(a), a conventional ramp 20 includes a mount 21 having a screw pit 25 therein for fixing of the ramp 20 to a housing of an information recording disk apparatus with a screw, and also includes an arm holder 22. The arm holder 22 has accommodation zones 27 in which a slider having a magnetic head mounted thereto for writing or reading to or from a recording disk is held as spaced from the associated one of the recording disks, and also has guiding parts 28 for facilitating access of the suspension arm to the accommodation zones 27 by sliding associated lifting projection.
The mount 21 and arm holder 22 are integrally molded by once injection molding operation with use of polymeric material containing the PTFE. A metal sleeve 30, which is inserted into the screw pit 25 and then molded, acts to less transmit a stress accumulated in the vicinity of the screw pit 25 at the time of tightening the screw to the polymeric material part.
The mount 21 is made up of the screw pit 25, the metal sleeve 30, and a bracket 23 provided therearound.
The arm holder 22 is supported by the accommodation zones 27 for storage of the lifting projections of the suspension arm associated with upper and lower surfaces of each recording disk, the guiding parts 28, and a support 24 so that the accommodation zones 27 and guiding parts 28 are aligned in a disk stacking direction.
The accommodation zones 27 and guiding parts 28 are provided not only at upper surface sides shown in FIG. 11(a) but also even at lower sides of horizontally-symmetrical surfaces of each disk. A part of a peripheral edge of each disk is entered into associated one of openings 26. In other words, a front end edge 29 of each guiding part 28 and each disk within the openings 26 have a positional relationship that the edge and disk are located within the opening in a non-contact condition. The ramp 20 is fixed to the housing by means of a screw so as to satisfy the above positional relationship. As an actuator assembly is rotated in a direction away from the recording disk, the lifting projection mounted to the suspension arm is raised in the vicinity of the front end edge 29 of the associated guiding part 28, so that the arm is slid along the guiding parts 28 and stored into the associated accommodation zone 27. Further, as the actuator assembly is rotated in a direction opposed to the above direction, the lifting projection comes out of the accommodation zone 27, slides along the guiding part 28, and then released from the front end edge 29 of the guiding part 28 onto the disk.
In the case where the ramp 20 shown in FIG. 11(a) is fixed to the housing of the information recording disk apparatus by means of the screw, tightening of the screw causes a stress to be accumulated in the vicinity of the screw pit 25 in the mount 21. For the purpose of lightening the tightening stress of the screw, the metal sleeve 30 is used. However, even when the metal sleeve 30 is used, injection molding is carried out at the time of molding the ramp 20 under a condition that the sleeve 30 is placed within a mold at a controlled predetermined high temperature. For this reason, a stress (thermal stress) based on a temperature difference upon the molding is accumulated in the vicinity of the metal sleeve 30 in the ramp 20. In particular, when the mold temperature is once increased to a temperature of 80 to 90xc2x0 C. close to an upper limit of usable temperatures of the hard disk drive apparatus and then returns to room temperature upon the molding, the thermal stress, similarly to the screw tightening stress, will cause the front end edge 29 of the guiding part 28 to be deformed.
The stress irreversibly deforms the periphery of the ramp 20 with time passage or after the ramp is once increased to a high temperature, which involves dimensional misalignment of parts of the ramp 20. That is, the stress caused by fixing the ramp 20 by means of the screw will involve a creep deformation. The creep deformation is remarkable and problematic in the ramp 20, in particular, in the screw pit 25 and the front end edge 29 of the guiding part 28.
Further, in order that the front end edge 29 of the guiding part 28 smoothly guides the suspension arm 14 on the recording disk rotating at a high speed into the associated accommodation zone 27 or conversely smoothly guides the suspension arm 14 (especially, lifting projection 15) accommodated in the associated accommodation zone 27 onto the recording disk rotating at a high speed, it is required that the front end edge 29 of the guiding part 28 be located in such a position as not to be contacted with the recording disk and not to be spaced therefrom too much. That is, the front end edge 29 of the guiding part 28 is required to be positioned in a predetermined distance range with respect to the recording disk. For this reason, the guiding part 28 must be located at a position suitable for guidance of the suspension arm 14.
When creep deformation takes place in the vicinity of the screw pit 25 of the mount 21, however, its influence causes deformation of the guiding part 28 and the front end edge 29 of the guiding part 28 as mentioned in connection with FIG. 11(b), with the result that the front end edge 29 cannot be within the predetermined distance range with respect to the recording disk. As a result, the ramp 20 and recording disk are easily brought into contact by an external shock, thus disadvantageously resulting in generation of polymer particles.
Explanation will next be made in connection with a case where the front end edge 29 of the guiding part 28 becomes out of the predetermined distance range with respect to the recording disk 17, with reference to drawings.
FIG. 12 is a sectional view of the ramp 20, suspension arm and recording disk of FIG. 11(a) showing a positional relationship thereamong. In FIG. 12, the ramp 20 is fixed to the housing 11 of the information recording disk apparatus by means of a screw 31. Also illustrated in FIG. 12 are three recording disks 17(A), 17(B) and 17(C) arranged as extended into the ramp 20 in a non-contacted relationship therewith as well as the suspension arms 14 as spaced from the associated recording disks 17 by the associated guiding part 28. Although members in FIG. 12 are illustrated with spaces therebetween for the purpose or easy distinction therebetween, the lower surface of the bracket 23 may be brought into contact with the lower surface of the support 2 as an example so that the ramp 20 is supported by the housing 11.
That the front end edge 29 of the guiding part 28 is located to be out of the predetermined distance range with respect to the recording disk may sometimes mean that distances L1up and L1down between the upper and lower surfaces of the recording disk and associated cutout parts of the ramp 20 are not equal to each other. And when one of the distances L1up and L1down becomes too much small, an external shock applied to the hard disk drive apparatus in operation may cause easy contact between the recording disk 17 and ramp 20, which possibly causes a harm in the reading and writing of magnetic record.
Since the distances L1up and L1down become not equal to each other, loading and unloading positions of the sliders (heads) on the same recording disk, which are installed on the upper and lower surfaces thereof, are shifted remarkably. An recordable area on the recording disk is determined by one of the heads having larger one of distances L2. That is, when the loading and unloading positions of the sliders (heads) on the recording disk are moved in an inner peripheral direction of the disk, the recordable area on the disk is decreased. Thus for the same recording density, the overall capacity is disadvantageously decreased.
In an extreme example of the actual hard disk drive apparatuses, a movement of the front end edge 29 of the guiding part 28 may cause recorded date not to be able to be read out therefrom.
In FIG. 12, both the lifting projection 15 at a position raised by the guiding part 28 and the lifting projection 15 positioned on the recording disk 17 are illustrated for convenience of explanation.
A disadvantage that the front end edge 29 of the guiding part 28 becomes out of the predetermined distance range with respect to the recording disk 17, tends to occur when the recording disk 17 is rotating at a high speed, that is, when the interior temperature of the information recording disk apparatus is high. This is considered to be caused by the reason which follows. That is, the polymeric material has a thermal expansion coefficient as large as several to several tens of times the thermal expansion coefficient of a metallic material. Thus when the front end edge 29 of the guiding part 28 in the ramp 20 having the recording disk 17 rotating at a high speed is deformed due to the thermal expansion, the influence of the aforementioned thermal stress or screw tightening stress will change its deforming direction.
The more the number of such recording disks 17 stacked within the information recording disk apparatus 10 is increased, the more easily the disadvantage of the front end edge 29 of the guiding part 28 going out of the predetermined distance range with respect to the recording disk 17 takes place. The reason of this disadvantage is explained as follows. As the number of recording disks increases, the dimension of the ramp 20 in a direction overlapped with a plurality of recording disks is increased. For example, when six of the front end edges 29 in FIG. 12 are denoted by reference symbols A1, A2, B1, B2, C1 and C2 sequentially from the upper side of the magnetic recording disk apparatus toward the lower side of the apparatus contacted with the housing 11, a distance L3 between the front end edge 29 (C2) of the guiding part 28 associated with the lower surface of the lowermost disk C and the front end edge 29 (A1) of the guiding part 28 associated with the upper surface of the uppermost disk A is increased, and the amounts of the front end edges 29 (A1), 29(A2), 29(B1), 29(B2), 29(C1) and 29(C2) of the guiding parts 28 deformed by the thermal expansion will be correspondingly increased.
FIG. 13 is a diagram showing a relationship between the temperature and deformation of the front end edge 29 of the guiding part 28 in the conventional ramp of FIGS. 11 and 12.
In FIG. 13, the deformed amounts of the six front end edges 29(A1), 29(A2), 29(B1), 29(B2), 29(C1) and 29(C2) in FIG. 12 were measured.
As shown in FIG. 13, when a change (a differential dimension xcex94L based on the deformation of the distance L3 in FIG. 12) in an interval between a front end edge A1 and a front end edge C2 is about 85 xcexcm for 100xc2x0 C. The larger the number of such recording disks 17 laminated in the information recording disk apparatus is, the larger the interval value is as mentioned above, which becomes a serious problem.
In the prior art, the deformation direction of the front end edge 29 of the guiding part 28 has been considered to be only a P direction. For this reason, there has been considered a method for suppressing the deformation amount of the front end edge 29 in the P direction by making a junction hole in a metallic plate (stainless plate) having a small thermal expansion coefficient at a given position, blanking it into such a shape as to be accommodated within the support 24 and inserting it into the support 24.
FIG. 14 is a diagram showing a relationship between the amount of deformation in the front end edge 29 of the guiding part 28 in the conventional ramp and the temperature thereof, when the number of recording disks is six that is twice that of the prior art example of FIGS. 11 to 13 and when the metallic plate is inserted into the support 24.
In FIG. 14, as in FIG. 13, the amounts of deformation in the front end edges 29 (A1, A2, B1, B2, C1, C2, D1, D2, E1, E2, F1 and F2) of the twelve guiding parts 28 corresponding to a total number of upper and lower sides of six recording disks were measured with respect to changes in the ambient temperature. Further, it was assumed that L6 denotes a length of an interval between the front end edges 29 (A1 and A2) of the guiding parts 28 corresponding to the upper and lower sides of the first recording disk A, L7 denotes a length of an interval between the front end edges 29 (B1 and B2) corresponding to the upper and lower sides of the second recording disk B, L8 denotes a length of an interval between the front end edges 29 (C1 and C2) corresponding to the upper and lower sides of the third recording disk C, L9 denotes a length of an interval between the front end edges 29 (D1 and D2) corresponding to the upper and lower sides of the fourth recording disk D, L10 denotes a length of an interval between the front end edges 29 (E1 and E2) corresponding to the upper and lower sides of the fifth recording disk E, and L11 denotes a length of an interval between the front end edges 29 (F1 and F2) corresponding to the upper and lower sides of the sixth recording disk F.
As shown in FIG. 14, since the metallic plate is inserted into the support 24, a change (xcex94L in the interval L6 between the front end edges A1 and F2) in the interval between the front end edges A1 and F2 is about 40 xcexcm that is half or less of the change in FIG. 13 even for 100xc2x0 C. That is, the deformation amount is decreased down to such a level as not to cause a problem with the entire ramp. However, a change in the interval L6 is about 35 xcexcm, a change in the interval L7 is about 36 xcexcm, a change in the interval L10 is about 35 xcexcm and a change in the interval L11 is about 35 xcexcm. Accordingly when such changes are viewed from each recording disk, the problem with the amount of deformation in the front end edge 29 of the guiding part 28 will not be decreased sufficiently down to such a level as to less cause a problem.
Further, for the purpose of suppressing the amount of deformation in the front end edge 29 of the guiding part 28, a mount is prepared by continuously molding two sorts of color polymeric materials having small thermal expansion coefficients (which will be referred to merely as xe2x80x98two-color moldingxe2x80x99) different from the thermal expansion coefficient of an arm support to suppress the amount of deformation of the front end edge 29 in a P direction, as disclosed in Japanese Patent Application No. 2000-31985 by the same inventors as the present application.
However, it has been found from studies of the inventors of the present application that the front end edge 29 of the guiding part 28 is deformed in three directions, that is, not only the stacked direction (P direction) while keeping parallel to the plane of the recording disk but also a direction (Q direction) that the front end edge 29 momentarily opens and moves (curled up) away from the recording disk plane and a direction (R direction) the side end edge in the vicinity of the front end edge 29 momentarily opens and moves (curled up) away from the recording disk plane. Thus for the purpose of suppressing the deformation amount, it has been found that, in addition to taking a prior art measure against the P-direction deformation, it is required to take a measure against the deformations in the Q and R directions.
The deformation of the front end edge 29 in the Q or R direction is considered to caused from the deformation of a beam 40 in a Z direction shown in FIG. 11(b), in particular, by the thermal expansion of a beam 40 which is made of the same material as the guiding part 28 and which bridges two guiding parts 28 disposed back to back in the disks stacking direction.
In the case where the metallic plate is made of material having a small thermal expansion coefficient or is two-color molded, further, it is believed that, when an engagement position engaged between the guide made of material having a large thermal expansion coefficient and the metallic plate having a small thermal expansion is coefficient is moved away from the front end edge 29, a part of the guide corresponding to a moment arm is extended, thereby increasing the amount of deformation in the Q or R direction.
In addition, the momentary deformation, in particular, in the R direction is considered to be increased when the transversal width dimension of the front end edge 29 of the guiding part 28 corresponding to a moment arm is large.
It is therefore an object of the present invention to provide a ramp which can lighten or eliminate a cause of increasing the aforementioned deformation to thereby decrease the deformation of a front end edge of a guide caused by thermal expansion, in particular, not only the amount of deformation in a disk stacked direction but also the amounts of deformation in a direction in which the front end edge momentarily opens and in a direction in which a side end edge of the front end edge momentarily opens.
In accordance with an aspect of the present invention, the above object is attained by providing a ramp for use in an information recording disk apparatus wherein the amount of deformation in the front end edges of guiding parts caused by thermal expansion. The ramp includes at least two guiding parts individually formed for each suspension arm and made of a polymeric material having a small friction coefficient for guiding the suspension arm by sliding into a accommodation zone, and a guide supporting member made of a material having a thermal expansion coefficient smaller than that of the polymeric material of the guiding part for supporting each guiding part at a predetermined position. The guide supporting member has first engagement parts, the first engagement parts are located in zones to be contacted with the associated guiding parts and are not contacted with associated recording disks. The first engagement parts are engaged with the associated guiding parts at such positions that distances to the front end edges of the guiding parts become shortest, each of the guiding parts has a second engagement part, and when the second engagement part is engaged in the associated first engagement part, the guiding part guides the suspension arm at a suitable position.
In the ramp for use in the information recording disk apparatus, further, no bridging member made of the same material as the each guiding part for linking a support surface of each guiding part and a surface of the guiding part opposed thereto is provided at least between the front end edge of the each guiding part and the second engagement part.
In the ramp for use in the information recording disk apparatus, the front end edge of the guiding part is set to have such a minimum width that causes the suspension arm not to be brought into contact with the guide supporting members. The guide supporting member is engaged with the guiding part at such an angle that the suspension arm is not contacted therewith, or is made in the form of an arc so that the suspension arm is not contacted therewith and is engaged with the guiding part.
In the ramp for use in the information recording disk apparatus, the guide supporting member is made of a metallic plate and the second engagement part of the guiding part is provided with a anti-lean support part so that the opposing surfaces of each guiding part are not linked mutually.
In the ramp for use in the information recording disk apparatus, the guide supporting member is provided with a comb shape in a part other than escape parts of the recording disks, the comb being extended to the front end edges of the guiding parts.
In the ramp for use in the information recording disk apparatus, the guide supporting member is made of a polymeric material which has a thermal expansion coefficient smaller than that of a polymeric material of the guiding part.
In the ramp for use in the information recording disk apparatus, the guide supporting member has guide gaps of such a shape as to fill gaps between the guiding parts on their sides where the suspension arm is not slid.
In the ramp for use in the information recording disk apparatus, the first engagement part is provided in the guide supporting member corresponding to the guide gaps, and the second engagement part is provided to the guiding part at a position opposed to the first engagement part.
In the ramp for use in the information recording disk apparatus, the first and second engagement parts are of a hook type where the first and second engagement parts are combined into a hook.
In accordance with another aspect of the present invention, there is provided an information recording disk apparatus having the ramp as set forth in the above. The disk apparatus includes a rotary actuator assembly linked with a suspension arm, a plurality of laminated magnetic disks, the ramp disposed in the vicinity of the magnetic disks for retracting the suspension arm, and a housing in which the actuator assembly, magnetic disks and ramp are accommodated.